Electronic register for telephone switching systems



Feb. 9, 1954 N. I. HALL ETAL 2,668,931

ELECTRONIC REGISTER FOR TELEPHONE SWITCHING SYSTEMS Filed D86. 20, 1949 10 Sheets-Sheet 1 JUN C TOR COMMON RELEASE AND TIME OUT CIRCUIT LINE AND LINE- L/NK FIGS F/G.6

N. HALL INVENTO/PS G. HECHT C. 0. K0 CHL/NG A 7" TORNEV FIG.

10 Sheets-Sheet 2 lllll l Feb. 9, 1954 N. 1. HALL ET AL ELECTRONIC REGISTER FOR TELEPHONE SWITCHING SYSTEMS Filed Dec. 20, 1949 ATTORNEY Feb. 9, 1954 N. 1. HALL ET AL ELECTRONIC REGISTER FOR TELEPHONE SWITCHING SYSTEMS l0 Sheets-Sheet 3 Filed Dec. 20, 1.949

MI. HALL INVENTORS 6. H5077 C. D. KOECHLING A TTORNE V 4 N. 1. HALL ET AL 2,668, 3

ELECTRONIC REGISTER FOR TELEPHONE SWITCHING SYSTEMS Filed Dec. 20, 1949 10 Sheets-Sheet 4 N. I. HA L L lNl/iF/VTORS G. HE Ch'T C. D. KOECHL IWG BYJWMW A TTORWE Y FIG. 4

Feb. 9, 1954 N. l. HALL ET AL ELECTRONIC REGISTER FOR TELEPHONE SWITCHING SYSTEMS Filed Dec. 20, 1949 10 Sheets-Sheet 5 /v. I. HALL uvvmrons a. HECHT c. a. KOECHL/NG (7 ATTORN EV 9, 1954 N. 1. HALL ETAL 2,668,931

I ELECTRONIC REGISTER FOR TELEPHONE SWITCHING SYSTEMS Filed Dec. 20, 1949 10 Sheets-Sheet 6 I Ml. HALL lNVENTO/PS G. HE'CHT CD. KOECHL/NG sky A TTO/PNE V Feb. 9, 1954 N. l. HALL ETAL 2,668,931

ELECTRONIC REGISTER FOR TELEPHONE SWITCHING SYSTEMS Filed Dec. 20, 1949 10 Sheets-Sheet 7 ENTORS k 9 WV cfa. KOECHLING AT TORNEV Feb. 9, 1954 N. l. HALL ETAL ,668,93

3 ELECTRONIC REGISTER FOR TELEPHONE SWITCHING SYSTEMS 1 Filed Dec. 20, 1949 10 Sheets-Shet s gimmi- Feb. 9, 1954 N. l. HALL ET AL ELECTRONIC REGISTER FOR TELEPHONE SWITCHING SYSTEMS 10 Sheets-Sheet 9 Filed Dec. 20, 1949 N. I. HALL INVENTORS G. HECHT BY C. D. KOECHL/NG ATTORNEY 1954 N. HALL ET AL. 2,668,931

ELECTRONIC REGISTER FOR TELEPHONE SWITCHING SYSTEMS Filed Dec. 20, 1949 10 Sheets-Sheet 1o N. I. HALL INVENTORS G. HECHT C. D. KOECHL/NG BY) 2 Z A 7' TOR/V5 Y FIG. /0

Patented Feb. 9, 1954 UNITED STATES PATENT OFFICE ELECTRONIC REGISTER FOR TELEPHONE SWITCHING SYSTEMS Application December 20, 1949, Serial No. 134,107

26 Claims.

This invention relates to telephone switching systems, and more particularly to circuits and apparatus for counting and storing dial pulses and for performing control functions in response thereto.

An object of this invention is to provide an electronic dial pulse counting, storing and responsive system of high efiiciency and rapidity of operation.

Another object of this invention is to provide an electronic register capable of properly responding to a plurality of diverse normal and abnormal conditions.

A feature of this invention is a pulse counting chain embodying certain novel provisions.

Another feature of this invention is an electronic counting chain for counting the dial pulses representing each digit of a telephonic designation and electronic storing means for storing the successive digital representations.

Another feature of this invention is an electronic progress means operable successively to associate a pulse counting chain with several electronic digit registers. A further feature of this invention is an electronic control means operative at the first dial pulse representing each digit and another electronic control means operative at the end of the dial pulses representing each digit of a telephonic designation.

Another feature of this invention is an electronic means operative in response to the receipt of pulses representing a selectable first digit for preventing the counting or storing of subsequent dial pulses.

Another feature of this invention is an electronic means operative in response to the receipt of pulses representing a selectable first digit for clearing the counting and storing means of that digital representation and for thereafter permitting subsequent dial pulses to be counted and stored.

A more complete understanding of the abovementioned and other features of the invention may be obtained from the following detailed description of the functioning of an illustrative embodiment thereof, when read with reference to the accompanying drawings, in which:

Figs. 1 and 2 are representations of other elements of a system with which the subject register may be associated;

Fig. 3 discloses a progress chain operable successively to associate a certain portion of the register circuit with certain other portions of the register circuit;

Fig. 4 discloses the counting chain by means of which incoming pulses are counted, and certain additional equipment;

Figs. 5, 7 and 8 disclose certain control apparatus comprising a part of the register;

Fig. 6 discloses the storing means for the hundreds, tens and units digits and certain additional equipment;

Fig. 9 discloses time-out means for the register;

Fig. 10 discloses certain class-of-service control relays in the register; and

Fig. 11 shows the manner of arranging the several figures of the drawing.

Throughout the specification the circuit elements will be identified by functional designations followed by a number in parenthesis representing the figure of the drawing upon which that element appears. For example, the offnormal relay in Fig. 5 of the drawing will hereinafter be designated relay ON(5) The eight-element electron discharge devices utilized in the disclosed preferred embodiment of the invention are cold-cathode gas-filled tubes preferably of the type more fully disclosed in Patent 2,549,064 granted April 17, 1951, to W. A. Depp. As shown for example in Fig. 5, tube RA(5) comprises two control anodes 5! and 502, two control cathodes 503 and 504,. a main cathode 505, and three main anode 506, 501 and 508. In general, the application of a suitable potential difference between either the control anode 50! and control cathode 503 or between the control anode 502 and control cathode 504 will cause a discharge to occur across the control gap therebetween. With a suitable voltage applied to any one of the main anodes 505, 501 or 508, the control gap discharge will be transferred so as to exist between the control cathode 503 or 504 and the main anode 506, 501 or 500. If the main cathode 505 is at a voltage sufficiently negative in respect to the control cathode 503 or 504, the discharge will then transfer to the main gap so as to exist between the main cathode 505 and the main anode 506, 501 or 505. This sequence will hereinafter be referred to as a control gap discharge followed by first and second transfers of discharge.

Since rapidity of operation is an object in any telephone system, it may here be noted that pro vision is made to decrease the ionization time of certain of the critical gaseous discharge tubes employed in the system herein disclosed. For example, the circuit of tube RA(5) is arranged so that a minute keep-alive circuit flows across the right-hand control gap thereof while that tube is in its non-conducting state. Prior to the time that a suitable positive potential is applied to the left-hand control anode 501 as will be described hereinafter, a suitable main anode potential, such as positive 135 volts, is applied to the left-hand main anode 506 over a path hereinafter to be traced. This potential is also applied to the right-hand control anode 502 of the tube. The right-hand control cathode 594 of tube RA() is connected to negative battery, which may supply a negative 48-volt potential, through resistor 509 and through the winding of relay RA(5). Resistor 509 should have .a high value of resistance as indicated. in the drawing. In

the disclosed embodiment, with the potentials applied, and with the characteristics of the par-- ticular tube utilized, resistor 509 has been found to best serve its function if its resistance is ap proximately 22 megohms. With these applied potentials and with high resistance resistor 509 in the external circuit, a current of a few microamperes flows across the right-hand control gap of tube RA(5), i. e., between control anode 5512 and control cathode 504. This current is maintained at a value below the threshold current of the tube, but is such that upon the application of a suitable potential difference across the lefthand control gap of the tube, breakdown will occur considerably more rapidly than would otherwise be the case. This keep-alive current is interrupted when the main anode voltage is removed, as will be described hereinafter.

Referring now to Figs. 1 and 2 of the drawing, a representation is presented of an exemplary telephone switching system with which the subject system may be associated. A suitable representative system is disclosed and described in detail in Patent 2,666,096, granted January 12, 1954, to W. A. Cornell, N. I. Hall, G. Hecht, C. D. Koechling, F. A. Korn, and H. E. Powell, and the disclosure of that patent is hereby made a part of this specification by reference. The subject-matter of this application is also disclosed and described in the above-cited application W. A. Cornell et al. patent.

.S'ciez'ng the junctor and register In general, in the representative telephone system of Figs. 1 and 2, the lines from the subscribers stations appear in the system at the line and line-link circuit (Fig. 1). When a calling subscriber desires to initiate a call, he will lift the receiver or remove the handset from its cradle. The line and line-link circuit is operative in response to that closure of the subscribers loop to extend the calling partys line to one of a plurality of junctors, one of which is represented partially in detail in Fig. l. The calling subscribers tip, ring and sleeve conductors appear at the left of the junctor as conductors I01, 102 and 103, respectively. The tip conductor 101 is extended through the No. 1 contact of unoperated relay CO(I) and to ground through the upper winding of supervisory relay S0). The ring conductor 102 is extended through the No. 6 contact of relay CON) and to battery through the lower winding of relay S( 1 The line and line-link circuit then signals the common release and time-out circuit (Fig. l) which transmits a signal over conductor 1% which is cabled to Fig. 7, No. 6 con-tact of 'unoperated register off-normal relay ON1(1), conductor 101, No. 1 contact of unoperated relay 'IM(9), conductor 901, through the closed con 4 tacts of switch 102 and to conductor 103 which is extended to the register connector of Fig. 2. In a similar manner, the common release and time-out circuit transmits a signal over a similar path in all (other of the provided register (not shown) which are idle, andto the register connector. The register connector will then select one of the idle registers for use on this call, herein assumed to be the register shown in the drawing.

The line and line-link circuit then grounds the calling subscribers sleeve lead, which appears at the J'unctor (Fig. l) as conductor 103. This ground on conductor 103 is connected to battery through the winding of the junctor ofinormal relay ON(I') whereby that relay is operated to indicate that this junctor is busy. The

path for the register start relay ST(5,), which path may be traced from battery, upper winding of unoperated relay 00(1) in thejunctor (Fig. 1),, conductor '10! which is extended through the operated register connector (Fig. 2) and to Fig. 5, winding of relay ST CE), resistor 511, conductor 512, No. 5 contact of unoperated relay CM (71),, conductor "102 and to ground through either the No. 2 contact of relay TM(:9D or the No. 4 contact of relay NGT(9) The resistance in this circuit is such that insufiicient current flows to operate relay CO(1) in the junctor, but relay 8713(5) is operated.

Relay ST(5), in operating, connects, at its No. 2 contact, ground to conductor 513., resistor 5. through the biasing winding of pulsing relay L0.) and to battery, to ensure that relay L(5). is unoperated before being closed to the line, as will be described hereinafter. Relay ST(5), in operating, also closes ground through its No. 4 contact to conductor 515 to operate av trafficregister (not shown) in the line and line-link circuit (Fig. 1). The operation of this traflic register indicates that this equipment has been employed in originating a call. Relay ST(5), inoperating, also closes ground through its No. 1 contact to conductor 516, winding of relay STHS), and to battery. Relay 6771(5) operates and locks through its No. 4 contact, conductor 5:1], to groundthrough the No. 2 contact of relay 51345.).

Relay 'STI (5), in operating, closes ground through its No. 6 contact to conductor 5.1.8 which is cabled to Fig. .9, lower winding of relay TMAM), and to battery. The operation of relay TMAQ) closes the ground on conductor 518 through its No. 4 contact to conductor 902 to operate relay TMB(9). Since the operation of relay 'STi(-5) interrupts, at its No. 5 contact, theresistance shunt around capacitor 903 comprising conductors 004 and 905 and resistor 906, the operation of relay TMA(9) will close acharging path for capacitor 503 which may be traced from positive battery, resistor 901, across capacitor 903, conductor 900, No. 2 contact of relay TMA(9), and to negative battery. The rising potentialon capacitor 903 is'applied through resistor 908130 the left-hand control anode of timing tube TM(9). The control cathodes of this tube are connected through resistor BIG and the main cathode thereof is connected through resistor 9I5 to conductor 9G9. Conductor 909 is extended through the winding of relay TMGI), conductor 904, No. 2 contact of relay TMA(), and to negative battery. Therefore, at the lapse of a measured interval a discharge will occur across the left-hand control gap of tube Til (0) unless prior to that time relay STI (0) has released to release relays TMA(9) and TMBGJ) and to reestablish the resistance shunting path around capacitor 903. A time-out is thereby obtained whereby if the circuit functions by means of which relay STI is released do not immediately occur, the circuit will be released as will be described in detail hereinafter.

Relay STI (5), in operating, also closes ground through its No. 3 contact, conductor 52d, winding of relay ON(5) and to battery. Relay ON(5), in operating, completes a circuit from ground, No 4 contact of relay ON(5), conductor 52I which extends to Fig. 10, through the N0. 2 contact of relay FRHO), No. 2 contact of relay GL(I0), No. 1 contact of relay MRHD), No. 3 contact of relay CN (I0), No. '7 contact of relay OPRHIJ), No. 2 contact of relay T(I0), and to conductor IO0I which is cabled to the line and line-link circuit of Fig. 1. This ground on conductor IO0I causes the line and line-link circuit to transmit an indication back to the register as to the class of service to which the calling party has subscribed. This service may be non-restriated or restricted, i. e., the subscriber may or may not be permitted to call certain areas without additional charge. A plurality of methods of charging are also available, e. g., the subscriber may pay a flat rate for telephone service over a period of time or may pay on a messagerate basis. Therefore, the line and line-link circuit will connect, in effect, negative battery to one of the conductors IBM to IOI2 in accordance with the calling subscribers class of service. If that class of service be flat-rate non-restricted, negative battery will be connected by the line and line-link circuit to conductor I080, winding of class-of-service relay FRHB), resistor I 0I3, and to positive battery whereby relay FR(I0) will be operated. Relay FR(I0) looks operated through its No. 3 contact, resistor IIJI l, conductor I0l5 which is extended to Fig. 5, and to ground through the No. 8 contact of operated relay ON(5).

If the class of service be flat-rate restricted, negative battery will be connected to the line and line-link circuit to conductor I000, winding of relay CL5(I0) resistor IBIS, and to positive battery. Relay CL5(I0), in operating, completes a circuit from positive battery, resistor I0 I3, winding of relay FR(I0), No. 6 contact of relay CL5(I0), resistor Hill and to conductor Iiil5 which is connected to ground through the No. 8 contact of relay ON 5 as above described. It may be noted that relay CL5(I0) locks operated through its N0. 2 contact and resistor IUII to grounded conductor IOI5, and relay FR( :0) locks over the previously traced path.

Similarly, the trunk class-of-service relay T(I0), the operator relay OPR(I0), the coin relay CN(I0), the message-rate relay MRUIJ) and the grounded line class-of-service relay GL(I0) will be operated if the line and line link circuit transmits the signal over conductors I002, I003, I004, I005 or I001, respectively. Restricted service may also be provided on all but operators calls, with the application of the signal to conductor I006 operating relays CL2(I0) and MR(I0), to conductor I0l0 operating relays CL4(I0) and GL(I0), to conductor IOII operating relays GL3 I 0) and CN I 0) and to conductor IOI2 operating relays CLI(I0) and T(I0). The functioning of the restricted service relays CL-(IO) will be described hereafter.

Relay ON (5), in operating, also causes a shunt to be placed around the winding of relay ST(5), this shunt comprising conductor I0! at the left of the winding of relay ST(5), No. 7 contact of relay 0M5), conductor 522, No. 4 contact of relay CK('I), conductor I02, No. 5 contact of relay ONI ('I), conductor 5I2, and to resistor 5 which is connected to the winding of relay ST(5) completing the shunt. It may be noted that this shunt may be traced over an additional path in that conductor 522 also extends to the No. 1 contact of relay PS ('I), and from there the shunting path may be traced over conductor I04, No. 8 contact of relay TKfifl), conductor I05, No. 5 contact of relay VAC(8), conductor No. 8 contact of relay BYI (7), and again to con ductor I02 which extends as previously traced. The shunting of the winding of relay ST(5) and of resistor 5H reduces the resistance in the previously traced energizing path for relay ST(5), which included the winding of relay 00H) in the junctor, and relay CO(I) operates.

Relay CON), in operating, completes a circuit from ground at the No. 6 contact of relay TK(I conductor me, No. 3 contact of relay OOH), conductor H0 which extends through certain contacts, not shown, winding of relay SRiI), and to battery.

It will be recalled that the register connector was operated under the control of the line and line-link circuit over a path including the No. 3 contact of relay SR). Relay SRH), in operating, causes the register connector to be held operated under the control of the same relays in the register that hold relay CO( I) operated, i. c. it transfers conductor I 08, which i connected to the register connector, through the No. 4 contact of relay SRO) to conductor H12 which is connected through the No. a contact of relay CO(I) to conductor Iii'l which extends to ground in the register as above described. Relay SR( I), in operating, also connects ground through retard coil M3, N0. 5 contact of relay SE), to conductor Hi3 which is the sleeve lead, and thereby provides a holding path for relay CNN) in the junctor and for certain elements in. the line and line-lint: circuit.

Relay 00(1), in operating, transfers the subscribers tip and ring conductors from relay S( I) in the junctor to the register. The subscribers tip conductor enters the junctor as conductor IOI, and is connected through the No. 2 contact of relay OOH) to conductor H0, and through the No. 5 contact of relay RFH) to conductor H5. The subscribers ring conductor enters the junctor as conductor I02, and is connected through the No. 5 contact of relay CO( I) to conductor HE, and through the No. 9 contact of relay RFU) to conductor II'l. Conductors H5 and II! are cabled to the ringing connector in Fig. 2 and are connected through the back con tacts or the ringing connector hold magnet HOLDQ) to conductors Eill and. 2&2, respectively. These conductors are connected through the register connector (Fig. l) and then extend to Fig. 5. The extension 20I of the subscribers tip conductor is connected to ground through 7. winding 523 of the repeat coil, and the extension 202 of the ring conductor is connected through winding 524 of the repeat coil, and through the lower winding of relay 11(5) to battery, thereby operating relay 11(5).

Relay L65), in operating, closes .an energizing path for relay S=R( 5) which may be traced from ground at the No. 2 "contact of relay 1ON(5) conductor 525, front contact of relay L (5 conductor 526, No. .3 contact of relay Oil-( 5) conductor :52], resistor 528, winding .of relay SRCS) and to battery. It may be noted that the ground on comductor 527 is also extended through the No. .1 contact of relay CKU), resistor IDS, capacitor nu, and to negative battery. Capacitor ma thereby receives a charge which serves to delay the release of relay SECS) as will be .seen hereinafter.

Relay :SRL5), in operating, opens the previously traced locking path for relay ST! (5) through the No. .2 contact of relay react), and therefore when relay 'ST(5) releases as a result of the described shunting thereof, the energizing circuit for relay .STHJE.) will ;be interrupted and relay STHE) will be released. Relay STHfi), in releasing, will interrupt the previously traced energizing paths for relays TMA(9) and 'TMB(9) and those relays will release, interrupting the time-out. Relay ST! (5)., in releasing, also :opens the previously traced energizing path for relay ON(5), but that relay is held operated by the ground through the No. 4 contact of :operatedrelay SR (5). Relay ST! (5.) in releasing, also completes a path from ground through its No. 1 contact, conductor *5 29, No. 5 contact of relay SR(5), conductor 53B, winding of relay ONI (1,), and to battery. Relay ON I (1) operates and looks through its No. 4 contact and conductor 525 to ground at the No. 2 contact of relay ON (-5). Relay ON I (l), in operating, connects the source of dial tone, comprising alternator 109, through capacitor N0, N0. 9 contact of relay ONI (1), conductor "H I, No. 4 contact of relay AD(5), conductor 5-32, to ground through winding '533 of the repeat coil. Since the calling subscribers tip and ring conductors are connected through the windings 523 and 52A, respectively, of the re peat coil as before described, this signal is transmitted to the subscriber to indicate that dialing may proceed.

Relay N1 (1) in operating, also closes, through its No. 3 contact, ground to the off-normal ground conductor 112 which extends to various control relays in the register and which is represented by a dot-dash line in the drawing.

.Relay ON 1 (l), in operating, also causes the operation of the common release and time-out circuit in order that certain of the circuits other than the selected register and junctor may be prepared for additional calls. It will be recalled that the line and line-link circuit operated one of the class-of-serv-ice relays shown in the lower portion of Fig 1-0. Therefore, upon the operation of relay ONI (7) a circuit is completed from ground through the No.1 contact of relay FR( I 0.) or through the No. .1 contact of relay GL( H1) or through the No. 2 contact of relay MBHB) or through the No. 1 contacts of relays CNHD), OPRUO) or THO) to conductor [M9 which extends to Fig. '7, No. 7 contact of relay ONI (l), conductor 1 14, No. 2 contact of unoperated relay DC( conductor 536 which extends to Fig. '7 and is then cabled to Fig. l to the common -re lease and time out circuit. This circuit responds to perform the above-mentioned function but 8. does not disturb the established path from the calling subscribers line through the line and line-link circuit, junctor, register connector, and register.

Dialing PULSING As hereinbefore described, relay L(5) operates on its lower winding over the subscribers loop. Consequently, this relay will release response to the :dial pulses or momentary openings of the subscribers loop. The middle winding of the relay L65) is a biasing winding which opposes the lower or operating winding sufficiently .to force the relay to release when the loop is opened. The energizing path for this Winding'was previously traced. The upper winding of the pulsing relay 11(5) functions as an aiding winding, :assisting in both the operation and. release :of the relay. When relay L(5) is operated, capacitor 535 is charged over a path from negative battery, upper winding of relay L('5) capacitor 535, conductor .535, No. 5 contact of relay OAT-(5), conductor 531', front contact of relay L(5), conductor 525, No. 2 contact of relay ON (5) and to ground. When the subscribers loop i opened as by an opening of the dial contacts, relay L(5') will release thereby interrupting the charging path for capacitor 535 and permitting that capacitor to discharge through resistor 5'3 8 to negative battery. The current flow through the upper winding of relay .L(5) as a result of the discharging of capacitor 535, is .in a direction to aid the release of relay L65) and insures the closure of the .back contacts under adverse line conditions where the biasing winding alone might be insuillcient. When the subscribers looop is again closed, relay 11(5) again operates to complete the charging circuit for capacitor 535mm the current flowing through the upper winding of relay M55) as .a result of the charging of that capacitor aids the operation of the relay thereby ensuring a steady front contact closure.

As previously described, relay L(5'), in operating, closes parallel paths for the operatlonof relay SEAS) and for the charging of capacitor Jill. During the momentary release periods of relay L65), as a result of the momentary opening of the subscribers loop, the main energize ing path for relay 61%(5) is interrupted, but the discharging of capacitor 7151 through resistor Hi5,- No, ,1 contact of relay CK"), conductor 52?, resistor 528, and through the winding of relay SR6) suiiiciently delays the decay of enorgy in relay SPAS) so that that relay remains operated during these interruptions. On each operation of relay LLE), capacitor 101 again becomes fully charged so that relay SR/(S) willremain operated regardless of the number of dial pulse interruptions that occur.

Immediately prior to dialing, white relay LG) is operated, capacitor 539 becomes charged over a path from ground, winding 54-3 of the retard coil, capacitor 539, conductor 54!, No- 6 contact of relay ONIS), resistor 542, and to negative battery. At the receipt of the first dial pulse, comprising a momentary interruption of the sub-.- scr'ibers loop, relay L(5) will momentarily release, closing its back contacts. Capacitor 539 will therefore be discharged through the back contact of relay L-(5), conductor 525, No. 32 con-.- tact of relay ONCE), and to ground. The retard coil acts as an autotransformer with the windings 540 and "543 in series aiding. The negative portion of the stepped-up voltage oscilla-z tion is suppressed through rectifying element or varistor 544, and the positive portion is applied to conductor 545. The positive pulse on conductor 545 is conducted through the No. 3 contact of relay RA! (5) and through the No. i contact of relay DC( 5), in parallel, to conductor 545 over which it is employed to fire the counting chain tubes of Fig. 4. as will hereinafter be described. The positive pulse on conductor 540 is also conducted through the No. 5 contact of relay RA(5), resistor 541, No. 2 contact of relay AD(5), conductor 543, resistor till and to ground, thereby applying a positive potential to the lefthand control anode of tube Pl (5) for a purpose hereinafter to be described.

The pulse on conductor 5% is also applied to the left-hand control anode 5th of tub RA(5). The left-hand control cathode 503 of tube RA(5) is connected to negative battery through resistor 552 and through the winding of relay RA(5), and therefore a discharge will be initiated across the control gap of that tube. The lefthand main anode 505 of tube RA(5) is connected to a source of positive potential through the No. 8 contact of relay SR(5) conductor 555, through the No. 2 contact of relay NT(8) and through the No. 5 contact of relay NTI(8), in parallel, conductor 852, resistor 550, No. 4 contact of relay RA! (5), resistor 55!, and to the main anode 50B of tube RA(5). The main cathode 555 of tube RA(5) is connected to negative battery through the winding of relay RA(5). Therefore, upon the initiation of a control gap discharge in tube RA(5), first and second transfers of discharge will occur and relay RA(5) will be operated. Relay RA(5) is operated at the first pulse of each digit to indicate the beginning of each digit.

It Will be recalled that prior to the receipt of the first dial pulse, relays L(5) ON(5) and 81 5(5) were operated and relay RA(5) was unoperated. Under this condition, capacitor 553 is in a discharged condition, its discharging circuit being traced from ground, capacitor 553, resistor 55 i, conductor 555, No. 6 contact of unoperated relay RA(5), conductor 525, No. 2 contact of relay ON(5), and to ground. At the receipt of the first dial pulse, relay RA(5) is operated, as above described, to interrupt this path, but capacitor 553 continues to be shunted to ground through the back contact of released relay L(5), conductor 525, No. 2 contact of relay N(5), and to ground. At the termination of the first dial pulse, relay 13(5) again operates, removing this shunt, and permitting capacitor 553 to charge over a path from positive battery, resistor 555, No. 6 contact of relay 51 (5), conductor 555, resistor 554, capacitor 553, andto ground. This rising positive potential is applied through resistor 55'! to the left-hand control anode of tube RA|(5). The left-hand control cathode of tube RAH5) is connected through resistor 558, and the main cathode thereof is connected directly through conductor 559, winding of relay HA1 (5), to negative battery. The left-hand main anode of tube RAMS) is connected via conductor 550, upper back contact of relay EX(5), and resistor 55! to conductor 802 which is connected to positive battery as before described. Therefore, when capacitor 555 has charged to a sufiicient value, tube RAI(5) will discharge and undergo first and second transfers of discharge. The time constant of the network comprising capacitor 555,4resistor 554 and resistor 556 is such, however, that capacitor 553 will not be charged to the critical value during any of the intervals between the pulses representing any one digit. Therefore, if another pulse is immediately received in the course of the dialing of a digit greator than 1, relay L(5) will again release to reestablish the discharging path for capacitor 553. If the digit dialed be 1, or, in any event at the termination of the final dial pulse of the series representin any one digit, an appreciably longer delay will occur before the receipt of the next dial pulse. During this interdigital time, capacitor will charge to the critical value, tube RAHE will discharge and transfer, and relay RM (5) will be operated. Relay RAI (5), in operating, interrupts, at its No. 4 contact, the circuit supplying main anode battery to tube RA(5) that tube will be extinguished, and relay RA(5) will be released.

Relay RAI (5), in operating, also closes a circuit from battery, winding of relay EX(5) No. 1 contact of relay RAH5), No. 7 contact of relay DC(5), to off-normal ground conductor l l2 which is grounded through the No. 3 contact of relay ONHI) as hereinbefore described. It may be noted that capacitor 502 is charged through resistor 555 in parallel with the winding of relay EX(5) over the same path, the discharge of this capacitor upon the interruption of the energizing path for relay EX(5) rendering that relay slow to release.

Relay EX(5), in operating, interrupts, at its upper contact, the circuit for supplying main anode voltage to tube RA! (5), that tube is extinguished, and relay RA! (5) is released. Relay RAHE), in releasing, interrupts the previously traced energizing path for relay EX(5), and that relay releases. These operations occur during the interdigital time to restore the pulsing circuit and prepare it for the receipt of the next digit. The storing of the received digit and the restoring of the counting chain also occur at this time as will be described hereinafter.

Registering the digits The incoming pulses of each digit are first counted by means of the counting chain shown in Fig. 4, the first three digits are successively stored in the hundreds, tens, and units storing tubes, respectively, of Fig. 6, under the control of the steering circuit of Fig. 3, and the fourth digit, assuming a four-digit subscribers designation, is retained and stored in the counting chain of Fig. 4. One skilled in the art will be able readily to modify the disclosed and described circuits to provide for subscribers codes having a greater or fewer number of digits.

The counting chain comprises six tubes, via, RIBM), R21), R30(4), R40(4), R5505), and RAMA). The left-hand main anodes and the right-hand control anodes of the counting tubes Riifld) to R50(4), inclusive, are connected by conductor MI and resistor 402 to conductor 405; and the left-hand main anode and the righthand control anode of tube RA5(4) are connected by conductor 403 and resistor 405 to conductor 405. Conductor 405 extends to Fig. 5 and is connected through the lower back contact of relay EX(5) to conductor 802 which is supplied with -v01t positive battery as before described. The left-hand control cathode of tube Rl6(4) is connected to ground through a resistance-capacitance network comprising resistors 405 and 401 and capacitor 408, and the left-hand control cathodes of the counting tubes R2'H4) to R50). are connected to ground through similar individual networks; The left-hand control cathodeot'addfive tube RASM) is connected to-g-roundthrough resistor 409'. The main cathode of tube BMW) is connected through the network comprising resistor 4-H] and capacitor 4 to negative battery, and the main cathodes of the tubes R;2 'l '(4)- to R5!l(4), inclusive, are connected to negativebatterythrough similar individual resistance-capacitance networks. The main cathodeof tube RAMA-l is connected to negative battery through capacitor M5 and, in parallel therewith, resistor 416' and the Winding of' relay RA5(4'). It may be noted that the right-hand control cathode of each of the tubes in the counting chain is connected to its associated main cathode through a high resistor. For example, the right-hand control cathode of tube Rl6(4) is connected to the main cathode of that tube, andthereby to negative battery, through high resistor 411. Thus, the tubes in this counting chain are provided with keep-alive circuits toinsure the rapid operation thereof.

Prior to the receipt of the" first dial pulse of any digit, the left-hand control anode of tube R1614) is connected-through resistor 4 I8", through the network comprising resistor 4 9- and capacitor 420 through resistor 42 1, conductor 422, No. 2 contact of unoperated relay RAW), and con ductor 564 which is connected to point 565 on the Voltage divider comprising ground; resistor 555, No. 5 contact of relay DC('5)., conductor 561, No. 7 contact oi'rel'ay SR ("5), resistor 568*, and'positive battery. Therefore there is an approximately 50-voltpositive bias ontheleft-hand control anode of tube R1 8) before any dial pulse interruptions occur for any one digit; This potential is insufii'ci'en t to create a control gap discharge in the tube. The left-hand control anodes of the tubes R2164): to 1250(4), inclusive, are connected through similar networks and resistances to the maincathodes oi the immediately preceding tubes in the series. For example, the left-hand control. anode of tube R210!) is connected through resistor 425, through resistor 42B and capacitor 4.211 in parallel; and through resistor 428; to the main; cathode of tube B16 64); By these. connections, the left-hand. control anodes of. tubes R2'l(4.)",. 3338(4), R480! and Bill-(4:) are connected tov negativebattery- The left-hand control anode. of tube R-A5=(4) is: also connected to. negative battery through resistor 429', resistor 4-30 and resistor 43.4.

As previously described; upon the receipt of the first dial pulse, a high positive pulse is. transmitted: over conductor 546.1:0 the, counting chain tubes. This positive pulse is. applied through capacitors. 4232. to 4:33? and through. the. associated networks-to the left-hand controh anodes of tubes R-l:6('4;), R27(14 R38z(4)i, 1143 .64), R50), and RAB'UI respectively- The left-hand control anode of tube R125 (.4) hasbeenbiased positively, as previously described; and: the: left-hand con.- trolanodes. of: the: remaining tubes. R2164): to RAB (4)., inclusive, have; all beenbiasednegatively. Therefore, upon? the receipt of thefirst dial pulse, a dischargewill occur across. the left-hand control. gap.- of tube Rl-BM) only, and. first and; second transfers will immediately occur whereby conduction will existbetweenthe; main anode and the main cathode oftube Rl6=('4). When relay RAW) operates, also. in response to the receipt of the first pulse of the digit, the previously traced path for applying a positive biasto the left-hand control anode of tube- R16). is interrupted, and thiselectrodeis then connectedtq E2 the main cathode of tube R50) for: purposes of recycling as will be described hereinafter.

Glenduotion across the main gap oftube RN (4:) will result in an appreciablerise in potential at the maincathode thereof, as for example, from negative 48 volts to positive 50 volts. This rise inpotential is applied through resistor 428; through the network comprising resistor 426 and capacitor 427, and through resistor 425. to the left-hand control anode of the next. succeeding counting tube 1321(4); This rise in potential is delayed, however, to the extent of the charging time of capacitor Mil to permit the pulse on the control anodes to disappear to. obviate the possibility of tube R2l(4) being fired falsely. At thereceipt of the nextdial pulse, a positive pulse will be applied through capacitors 432 to 431 and to the left-hand control anodes of the. several counting chain tubes, and since tube R2114) is the only one thereof. having a suitable priming potential applied to. its left-hand control anode, that tube will undergo a discharge across: its left-hand control gap, and a. first and a second transfer will occur whereby conduction will exist across: the main gap. thereof.

At the instant of conduction in tube R2-.1('4)=, itsmain cathode will remain at. approximately 4'8 volts negative due to the presence of capacitor 439,. but. the potential at the main cathode of tube l d-6(4) will be at. approximately 50-. volts positive as previously described. The. additional drop across the common main anode resistor 402 as a resultof'the conduction. through tube.R21-'(.4 will: lower the potential at the main anodes of tubes R1|6(4) and R2164) to a point wherethe potential difference across the main gap. of tube RIZGUD is insufl'icien-t-to sustain. conduction, and tube Rl6(4) will be extinguished.

As capacitor 439 becomes charged, a. positive priming potential will be applied to the left-hand control anode of tube R38 (4) whereby thattube will be fired on the next dial pulse, extinguishingv tube R2l(4). Similarly, tubes R49)- and R5008) are successively renderedconductive, extinguishing the. previously conducting tube. With tube R5064) conducting as a result of live pulses having been received, the rise in main cathode potential: thereof will be applied through con.-

ductor 440;. through the Nos. 1 and 3 contacts 1 of relay RAG), and to conductors 5'19. and. 422 respectively. This. positive potential is applied over conductor 422, through resistor 42 I, through the network comprising resistor M9 and capacitor 420; and through resistor 418: to the lefthand control anode of tube RI 6(4) This positive potential is also applied over conductor 510, through resistors 43'!) and 429 to the left-hand control anodev of tube RAE). Therefore, on the sixth pulse, both tubes RAE ('4) and R15) will fire. Conduction in tube R|6'(4 will cause tube. R5ll(4=).- to be extinguished, but it; may" be noted: that tubeRASM) is providediv with an individual main anode impedance comprising re.- si'stor 404 and will not, therefore, be extinguished as a result of conduction in any of the other counting chain tubes. Subsequent dial pulses will be counted as before, with conduction continuing in tube RA5(4) to indicate that conduction through tube R2114) now represents the digit 7, that conduction through tube R38) new represents the digit 8, and so forth. Since relay RA5(4') is in the main cathode circuit of tube HA5), as. previously described, conduc t'ion across the mainv gapv of that tube will! result the operation of relay RA5('4).

It may be noted that further means are provided to insure the proper extinguishing of a preceding tube upon the firing of the next succeeding tube. As above described, with tube 1216(4) conducting and after capacitor M! has fully charged, the main cathode potential of that tube rises to approximately 50 volts positive, and this positive potential is applied to the left-hand control anode of tube R21). At the next pulse on conductor 546, tube RUM) is fired and tube Rl6(4) is extinguished. As capacitor 539 becomes charged the main cathode potential of tube R2701) rises to approximately 50 volts positive. As capacitor 4H discharges through resistor M0, the main cathode potential of tube 1216(4) falls again to approximately negative 48 volts. However, with the main anode of tube R21(4) having risen to approximately 125 volts positive, even after tube R210!) has undergone both transfers of discharge, a discharge will continue to occur between the main anode of tube R2701), left-hand control anode of tube RZlUi), resistor 425, through the network comprising resistor 426 and capacitor 21, resistor 42%, and through the network comprising resistor tie and capacitor 4| 1 to negative battery. liherefore', the left-hand control anode of tube BNO!) will remain at an approximately 50-volt positive potential while tube R2101) is conducting. At the next pulse on conductor 545, tube Rfltfli) will be fired, and the main anode potential of all of the counting chain tubes will drop to a low positive value, such as positive volts. Since the main cathode potential of tube R2701) has risen to approximately 50 volts positive, the main gap discharge in tube R2703) will cease. Since the left-hand control anode of tube Rfilfll) is also at a positive 50-volt potential, conduction between that control anode and the main anode will also cease. If the left-hand control anode were connected to negative battery solely through resistors, the potentials thereat would immediately drop to negative 48 volts, and if tube R2103) had not completely deionized a discharge might then occur between the left-hand control anode and the anode of tube R27 (:3). The capacitive elements are provided in the circuit of the left-hand control anode to obviate this possibility by providing a time delay network to hold that control anode positive sufliciently long for tube R270!) to become completely deionized. These considerations also apply to the other tubes in the counting chain.

It may also be noted that current-controlling means are associated with the left-hand control cathodes of the counting chain tubes. Thus. ground is connected to the left'hand control cathode of tube Riiiflt) through series resistor 496 and through the parallel combination of resistor ill! and capacitor 4%. This network serves to permit a large initial surge of current at the first transfer of discharge in the tube but thereafter serves to limit the conduction between the main anode and left-hand control cathode after the second transfer has occurred thereby serving to cause the conduction in the tube primarily to exist between the main anode and the main cathode thereof.

Storing and preliminary pulse absorbing As each of the digits of the assumed four-digit subscribers number is received, the pulses representing each digit are counted in the counting chain of Fig. 4 as above described, with relay BAG) operating at the beginning of each digit,

and relay RAI (5) operating at the end of each digit. As the first or hundreds digit is received and counted, it will be stored in the hundreds storing tubes HIGHS) to I-IA5(6), inclusive, and the counting chain is reset in preparation for the counting of the next digit. The second or tens digit is counted by means of the counting chain tubes Rlfifll) to RAE), inclusive, and is then stored in the tens storing tubes 116(6) to TA5(6), inclusive, and the counting chain is reset. The third or units digit is counted, and is then stored in the units storing tubes Ulfifli) to UA5(5), inclusive. The fourth digit, representing the ringing code, is both counted and stored in the counting chain tubes RIB) to RASM), inclusive. The successive transfer of the counted digits to their respective series of storing tubes is accomplished under the control of the steering tubes PR3), P2(3) and P.3(3) and the associated steering relays Pi (3), 192(3) and P3(3) As previously noted, the positive pulse on conductor 5545, resulting from the receipt of the first dial pulse representing the first digit to be transmitted, is conducted through the No. 4 contact of relay DC(5) and through the No. '3 contact of relay RAI(5) in parallel, to conductor 546. through the No. 5 contact of relay HA6), resistor 541, No. 2 contact of relay AD(5), conductor 548, and through resistor to ground whereby this positive pulse is applied to the lefthand control anode of steering tube Pl (3). The left-hand control cathode of tube P|(3) is connected to negative battery through resistors 302 and 303 and the winding of relay Pl (3). Therefore, a discharge will be initiated across the lefthand control gap of that tube. Since the lefthand main anode of tube Pl(3) is connected through resistor 384 to conductor 802 which is connected to a positive main anode battery supply a previously described, tube 1 1(3) will undergo a first transfer whereby conduction will exist between the main anode and the left-hand control cathode thereof. Since the main cathode of that tube is connected to negative battery through resistor 3G3 and the winding of relay PI (3) and also through capacitor 355, a second transfer will occur, conduction will exist across the main gap of the tube, and relay PI (3) will be operated. It may be noted that the right-hand control electrodes of this tube are connected as a keep-alive circuit similar to that previously described in order to expedite the discharge in the tube.

The operation of relay PR3) prepares a circuit whereby upon the operation of relay AD(5) (hereinafter to be described) a suitable negative potential will be applied to the control cathodes of the hundreds storing tubes over a path from negative battery, No. 5 contact of relay RAI (5), which operated at the end of the digit, No. 1 contact of relay AD(5), the operation of which has not as yet been described, conductor 51!, upper front contact of operated relay Pl (3), conductor 3126, and through resistor Eilll to ground whereby a negative voltage is applied through resistors 602 to to the left-hand control cathodes of the hundred storing tubes HIMB), 1121(6), H38(E), 1149(6), Il5ll(6), and HA5(6), respectively. Until relay AD(5) is operated, however, this path is not complete, and the first or hundreds digit cannot be transferred from the counting chain tubes to the hundreds storing tubes.

Relay ,AD(5) is provided so, that any preliminary pulse, transmitted by an, inadvertent gum- .15 his of the switchhoolr, for example, may be absorbed. If, after the first pulse is received and counted by tube RI'EM), a sufiicient delay ensues so that relay RA! is operated, this pulse will represent, that the first digit transmitted is 1. The operation of relay RAI(5) will cause the, operation of relay EX('5) as previously described. The operation of relay EX(5) will remove main anode battery from the counting chain tubes and tube R1601) will be extinguished.

Therefore, the circuits are returned to" their normal condition as if no pulse had been received. It. may be noted that. since such a preliminary pulse. is, thus absorbed, a subscribers number must. have, as itsfirst digit, :3, number other than 1.),.

If the first: digit received is, 2 or greater, tube RZH-i) willbe or will have been rendered conductive. during the counting of the pulses representing that digit. When that tube becomes conducting, the. rise. in cathode potential thereof is transmitted over conductor d ll, through the N20. 81 contact of relay AD(5) resistor 5-12, conductor resistor tit, and to the left-hand control anode of tube ADGS). Negative battery is supplied through the upper winding of relay AD(5J), No. 6 contact of relay AD(5)., and conductor 514' to the main cathode of tube AD(6), and through resistor 6H to the left-hand control cathode of that tube. The left-hand main anode of tube ADM) is connected through resister 5I2 to conductor 8% over which main anode battery is supplied as before mentioned. Therefore, tube AD(6) will undergo a control gap discharge and first and second transfers, and relay AD(5:) will be operated.

Relay AD(5) looks over a path from negative battery, upper Winding of relay AD(5), No. '7 contact of that relay, lower Winding of that relay, resistor 51% to conductor 802 through which the positive battery at the N0. 8 contact of relay 513(5) is supplied as before explained. Relay AD(5) willthereby remain operated under the control of relay SR(5). Relay AD(5) in operating andlocking, interrupts the supply of negative voltage to the cathodes of tube ADGB) thereby extinguishing that tube.

With relay AD(5) operated as a result of the receipt of a first or hundreds digit greater than 2, the above-described path for the supplying of negative battery to the left-hand control cathodes of the hundreds storing tubes through the upper contact of relay PI (3) will be completed. It may be noted that since relay- AD(5-) is locked operated, 1 may be used as the tens, units or ringing code digit. Relay AD(5), in operating, also interrupts, at its No. 4 contact, the circuit over which dial tone wa supplied to the calling subscriber.

Th main cathodes of the counting, chain tubes are connected to the left-hand control anodes of their corresponding hundreds, tens and units storing tubes. Thus, the main cathode of countme chain tube Rlfiflt) is connected by conductor 443. and through resistors 614, 615 and 616 to the left hand control anodes of the hundreds storing tube HUNG), of the tens storing tube TIME), and: of the units storing tube Ul6(6), respectively; Similarly, the main cathode of counting chain tube R27), is connected by con:- ductor 4'4! through individual resistors: to. the left-hand control anodes of tubes H27 ('B')-,,T2.'l?(.6'):, and U21(6). The other corresponding tubes; are similarly interconnected, including the main cathode of the add-five counting chain tube 516 RAE) being connected by conductor 4 through individual resistances to the left-hand control anodes of tubes HA5(6), TA5(6.) and UA5(6).

The main cathodes of tubes I-Il6(6), H2103), H38(6), H49(6), and 1150(6) are connected to a source of negative voltage through resistors 61] to 62l, respectively, and the main cathode of tube HA5(6)- is connected to negative battery through the winding of relay HANS) Similarly, the main cathodes of the tensstoring tubes Tliitfi) to TEENS), inclusive, are connected to negative battery through individual resistors, and the main cathode of tube TA5 (6) is connected to negative battery through the winding of relay TA5(6). And in a similar fashion the main cathodes of the units storing tubes Ui6(6) to U506) are supplied with negative battery, with tube UA5(6) having the winding of relay UAS-(fi) in its main cathode circuit.

It will be recalled that a positive voltage from the positive battery at the No. 8 contact of relay SR(5) is supplied to conductor 802. This. positive, main anode voltage is thereby connected through common resistor 623 to the left-hand main anodes of tubes Hlfifli), I-I2'l-(6), H38(.6), H49('fi) and H5905) and through individual. resistor 624 to the main anode of tube HA5=(6). Similarly, main anode voltage is suppliedto-tubes Tl6(6.) to T5005), inclusive, through the common resistor 625', and to tube TA5(6) through the individual resistor 626. Ina similar fashion, the main anodes of tubes Ul6(6) to U5IJ(6), inclusive, are connected to positive battery through resistor 62?, and the main anode of tube UAS-(G') is connected to positive battery through resistor 628.

It may therefore be seen that upon the receipt and counting of dial pulses representing a first or hundreds digit greater than 1, and upon the operation of relay RAI (5) during the interdigital delay period following the transmission of those pulses, discharge initiating and sustaining potentials are applied to the electrodes of. the hundreds storing tubes which are associated with conducting counting chain tubes. Letting it be assumed for the present that the called subscribers numerical designation is 236-2, the first or hundreds digit is 2, and counting chain tube R2l(4), only, will be conducting. The rise in main cathode potential of that tube will be transmitted to the left-hand control anode of hundreds storing tube 1121(6), and since. the left-hand control cathode of that tube is; connected to a source of suitable negative voltage through contacts of relays PR3), AD(5), and RAKE) as above described, a control gap discharge will be initiated in tube HZ'HB), and first and second transfers will immediately occur, whereby conduction will exist across the main gap thereof.

This transfer of the counteddigit to the storing tubes occurs during the period after relay RA! (5) is operated, and before relay EX(5-) operates. When relay EX(5) operates, the previously traced circuit for the supply of. main anode voltage to the counting chain tubes-RIB (4) to BASH!) inclusive, is interrupted, and thev conducting counting chain tubes will be extinguished. Under the assumed conditions, tube 1221(4) is the only counting chain tube which is conducting, and it will be extinguished. Since relay EXGi), in operating, cause the release-of relay RAKE) which,- in turn, interruptathe energizing path for relay EXWI), the counting"- 17 chain tubes must be extinguished before relay EX() again releases to reestablish the main anode supply. The charge on capacitor 562 in sures that relay EX(5) will be sufficiently slow to release for the counting chain tubes to become deionized to the required degree. I

As previously mentioned, the release of relay RAMS) releases relay RAG) which results in the discharge of capacitor 553 at the control anode of tube RAMS), and the circuit is prepared for the receipt oi the second or tens digit.

At the first dial pulse of the second or tens digit, a positive pulse is transmitted from the re tard coil over conductor 545, through the No. 3 contact of relay RA! (5) and through the No. 4 contact of relay DCGG) in parallel, conductor 5%, No. 5 contact of relay RA(5), resistor 541, No. 3 contact of operated relay AD(5), conductor 57?, lower front contact of operated relay Pl (3), conductor 35's, and through resistor 308 to ground, whereby this positive pulse is applied to the right-hand control anode of tube P2(3). Negative battery is supplied through the winding of relay P2(3), conductor 3529 and resistor 3H) to the main cathode, and through the additional resistor 3H to the right-hand control cathode of tube 1 2(3). It may be noted that negative battery is also connected through ca pacitor 312 to the cathodes of this tube. The main anode of tube 1 2(3) is connected to main anode battery through resistor 384 which is commonto tubes PIG; P2(3), Pli(3), and DC(5). When the positive pulse is applied to the righthand control anode of tube 1 2(3), 9. control gap discharge and first and second transfers will immediately occur. The main cathode of tube P2 (3 will be momentarily held at approximately negative battery potential by capacitor 3 l 2, while the main cathode of previously conducting tube Pl(3) will be at a considerably higher voltage since capacitor 3235 will have become fully charged. Therefore, in a manner similar to that in which the counting chain tubes operate and commutate, the additional drop across resistor 38? resulting from the conduction through tube P2(3) will drop the potential at the main anodes to a point where the potential difference between the main anode and main cathode of tube Pl (3) is below sustaining voltage, and that tube will be extinguished. As tube P2(3) continues to conduct, capacitor 3 i 2 charges whereby the main cathode potential of tube 192(3) rises so that tube 1 2(3) may be extinguished upon the subsequent rendering of tube PMB) conductive, and relay 1 2(3) is operated. The extinguishing of tube PR3) will release relay Pl (3), which will interrupt the circuit over which negative battery had previously been supplied to the control cathodes of the hundreds storing tubes Hi 6(6) to HA5 6), inclusive.

The first dial pulse of the second digit also operates relay RA( 5) as before and fires the counting chain tube RIG). Since 3 is the tens digit of the assumed called subscriber's number, two additional dial pulses will be received which will result in counting chain tube R38), only, being conductive. During the interdigital delay, capacitor 553 will charge, and tube RAI (5) will be rendered conductive, operating relay RA! (5) as previously described. Relay RAI (5). in operating, will complete a circuit from negative battery through the No. 5 contact of relay RAMS), No. 1 contact of locked operated relay AD(5), conductor 5", No. 6 contact of operated relay P2(3), conductor M5, and through resistor 629 to ground, whereby a negative potential is applied to the left-hand control cathodes of the tens storing tubes 116(6) to TAEGi), inclusive. Since counting chain tube name) is conducting, a positive voltage will be applied over conductor 445 and through resistor 538 to the lefthand control anode of tube Ti li it). Tube 138(6) will therefore be r ndered co niuctive to store the digit .3 as the tens digit of the called subscribers number. Relay ii -1(5) will be operated and released, relays BANE) and R-A(5) will be released, the counting chain tubes will be extinguished in preparation for the receipt of the next digit.

At the first dial pulse of the third or units digit, a positive pulse is again transmitted to conductor 5?! from which that pulse is passed through the lower back contact of released relay 3), conductor me, No. 7 contact of operated relay P2(3), conductor 3H, and through resistor M8 to ground. whereby the pulse is applied to the right-hand control anode of tube 1 3(3). This tube fires, transfers, extinguishes tube PMS) thereby releasing relay 1 2(3), and operates relay P3(3) in its main cathode circuit in a manner similar to that previously described in relation to the firing of tube 1 2(3) at the beginning of the second digit. The release of relay P2 (3) interrupts the circuit over which negative battery had previously been applied to the control cathodes of the tens storing tubes TIME) to TA5(E5), inclusive. The operation of relay i 3(3) prepares a circuit whereby upon the opcration of relay RA! (5) at the end of the third digit negative battery will be connected through the lower front contact of operated relay P3(3), conductor M9, and through resistor 832 to ground whereby the negative potential will be applied through individual resistors to the lefthand control cathodes of the units storing tubes Ulfifli), UZ'HB), U38(E), U49(5), 1355(6) and UA5(6).

Since the units digit of the assumed called subscribers number 236-2 is 6, six dial pulses will be received and counted by means of the counting chain. The sixth pulse will render both tubes RA5(4) and R16) conductive as herein before described. Full conduction in tube RA5(4) will cause the operation of relay RA5(4) which is in the main cathode circuit of that tube. The rise in main cathode potential of tube RI 6 (4) will be transmitted over conductor 443 and through resistor BIS to the left-hand control anode of tube Ul6(6). The rise in main cathode potential of tube RA5(4) will be transmitted over conductor 444 and through resistor 633 to the left-hand control anode of tube UA5(6). Therefore, upon the elapse of the requisite portion of the interdigital time and the resultant operation of relay RAKE), tubes Ul6(6) and UA5(6) will be rendered conductive to store the digit 6. Relay E X(5) will operate and release. the counting chain tubes will be extinguished, and tubes and relays RA! (5) and EMS) will be released in preparation for the receipt of the next digit.

Upon the receipt of the first dial pulse of the fourth or ringing code digit, a positive pulse is transmitted over conductor 5H, through the lower back contact of released relay PR3), con ductor 3| 6, No. 8 contact of released relay P2(3), conductor 325, upper front contact of operated relay P3(3), conductor 326, and through resistor 518 to ground, whereby the positive pulse is applied to the right-hand control anode of tube eiccspai 336(5). Since negative battery connected through the winding of relay f lL/(fi conductor his, through resistor to the main cathode of tube DCGE) and through resistor Sti to th hand control cathode of that as through capacitor 522 to these-cathodes, a discharge will occur across the right-hand control gap of tube 138(5), first second transfers will occur, tube 1 3(3) will be extinguished to the additional drop across resistor lay lit-3(3) will be released, and relay 338(5) w i be operated. The release of relay 22(3) interrupt the'circuitover which negativ had previously been supplied to the contl odes of the units storing tubes "U'i (Hi5) to inclusive.

Since the fourth 'or ringing code digit of the assumed subscribers number 233-2 is 2, counting chain tube arson will be rendered conductiye, and will remain conductive to store this "2 ringing code digit. At the pauseiollowing the last dial pulse'of digit, tube l-tai (5) will hrs and relay 3A1 (55) will beoperated. The cperation of relay RM (5) will cause the'extihction of conduction 'through tube RAG) and relay (ii) will be released. Relay lilXit), however, will not operate since its previously traced his path is interrupted at the No. '7 contact of relay DCTE') as a result of theoperation of relay 1353(5). "Sincerelay EXW') "d oes not operate, the main "anode circuits for tube RAMS) and for the counting chain tubes will not be interrupted. Therefore, tube RENE) "will remain conducting to store the ringing code digit 2 and relay RAKE) will not/be released. be noted that any further dialingwillbe ineffective in'that the pulse output cireui't from the retani coil comprising windings and is interrupted by the "openingjof the No. "3 contact of relay i (5) "and'by the openingof the contact of relay DC ii-l).

The conjoint operation of relays RAKE) 'and D C (5) closes an energizing circuit for relay DC! (1) which may bet'raced' fr'om negative battery, winding of relay DCI (7), conductor "iii, left-hand back contact of 'relayTMBe), com ducto'r; 9, No. 5'contac't of relay CK("i), conductor "i l 3,'I lo.'3 contact of operated relay 130(5) conductor 583, No. Z cont act or operated relay RAJ (5) to cit-normal "ground conductor H2 whichi's'groundedthroughthe No. 3contact of relay on! (1) L Relay no: (1) will therefore be operated to "perform functions hereinafter" to be described. 7 I As hereinbefore mentioned, provision is made fer; tin e out in "the event that relay ST! ('5) fails to release within aprescrib'ed time. Proyision is "a1s'o ma'de for the circuits to tim'e out if 'the subscriber fails'to startdialing within another, and preferably considerably longer, prescribed tii'na'orif a'series of digits none of'which is greater than lf are received, or if 'an extended delayperiod occurs during the dialing.

j If, at the'ti ne relay ONiCi) op'eratesat the seizure of the register, relay ST! (mhasreleasedto release relay TIMAG) which, in turn, has released relay TMB(9), theoper'ationof relay ONI('|) will close an operating circuit for relay 'T'MA 9) which may be traced fromgroun'd through the No. 3 contact of relay ONI ('1) off-normal ground conductor-l l 2,"t;hrough the right-hand back contact of relay TMB (9) conductor 1 2, upper windingof relay TMA(9), and-to negative'battery. Relay -TMA( 9) in operating, will lock operated seer a path" fromnegative-battery,- lower winding 1 and No. 3 contact of relay TMAW), conductor 5H3, no. 8 contact of relay ONI (1)., conductor "its, No. 5 contact of unoperated relay AD E to off hornial ground conductor H 2. This ground is also-extended through the Nos. 3 and 4 contacts of operated relay IMMQ) to conductor 992, through the winding of relay TMB(@) and to negative battery. Relay TMBGQ) operates 'to-interrupt the original operating path for relay TMA(9) Relay TMAGE) in operating, connects negativebattery through its No. 2 contact'to conductor set, through the winding of relay "Eh/fie) conductor 989, and through resistors and die to the main and control cathodes, respectively, of tube Tl\?l(9') This negative battery on conductor 904 "is also applied to the lower electrode of capacitor iii'i. Positive battery is connected through resistor 928, No. 1 contact of relay NGTQi) conductor '9-2Ifresistor 922 to the upper electrode of capacitor ell. this capacitor will begin to charge, with the rising potential thereon being applied through-resistor era to the right-hand control anode of tube TMGJ) As indicated, the time constant oi the network including capacitor Sill is preferably considerably greater than the time constant of thenetwork including capacitor $203. If relay TMAAQ) is not released within this time, a discharge will be initiated across the right-hand control gap of tube TMGi). It may be noted that if, upon seizure of the register, relay ONi (i) is operated prior to the time that relay TMA 9 is completely released as a result of the release of relay ST! (5) relay TMA(3) will immediately look over the above-traced locking circuit.

If dialing commences beforeoapacitor on has charged to the critical potential, relay ADM?) will be operated at the second dial pulse of thefirst digit, but the locking path for relay TMA(9) 'will be maintained during the dialing of that digit since conductor i226 is then connected to off-normal ground conductor H2 through the No. 4 contact'oi relay RA(5) which is operated at the beginning ofeach digit. At the end of the first digit, relay RA(e) releases thereby releasing relay TMAGH. The release of relay TMMQ) interrupts the energizing circuitfor'relay TMBW).

The release'of relay TMBGE) again closes theoriergizing circuit for relay TMALQ) to off-normal ground conductor H2, but relay TMB(9) is slow to'relea-se so'that capacitor 9|! may completely discharge through the circuit including resistor QZZ'and the No. 1 contact of relay TMA(9) prior to the reoperation of relay TMA(9). At the beginning of'the second digit, relay RA 5 operates to provide a locking path for relay TMAGB) and an'operating path for relay TMB(9) and-at the end'ofthatdigit-relay RAG) releases to release relay TMA(9) which releases relay TlviBfll),

which, in turn, reoperates relay TMAQD. This -cycle repeats aseach digit is received. At the completion of the last digit, relay TMA 9) is released at the releaseof relay RA(5). 'Relay I dZe-busy-vacant test When relay DCi (l) is operated, a circuit is closed from ground, No.- 3 contact of rela'yRSfl),

conductor hi2, No. 2 contact of relay-DCi (i) and to conductor 123 which isex'tende'd tothe commen "release and time-out circuitin Fig. 1.. 'Re- 

